Los cambios de estado en la educación infantil : ¿qué modelos emplea el alumnado en la construcción de explicaciones?

Se describen los modelos que quince niños (5-6 años) aplican ante situaciones en las que ocurre un cambio de estado semanas después de participar en un proyecto sobre el ciclo del agua. Como actividades se propusieron la evaporación de un líquido en un plato y la condensación del vapor del ambiente sobre una lata. Para la recogida de datos se emplearon cuestionarios y entrevistas grupales. Para el análisis de datos se construyeron categorías. Los resultados indican que todos los niños emplean modelos en los que la materia se conserva. Además, durante la actividad de evaporación se observa en los niños una incipiente visión corpuscular de la materia. Esto demuestra la importancia de implicar a los niños en la interpretación de fenómenos

Interpretaciones de los futuros maestros de Infantil sobre la materia y sus cambios

Se describen las interpretaciones de 52 futuros maestros de Educación Infantil acerca de la descomposición térmica del azúcar. Para la recogida de datos se diseñó un cuestionario basado en una estrategia POE. Los resultados muestran que, a pesar de existir una cierta progresión en el nivel de desempeño, al final de la actividad los futuros maestros siguen teniendo dificultades en el manejo de conceptos como átomo, molécula o partícula, esenciales para construir un modelo de reacción química

Alien Registration- Sesto, Maria (Portland, Cumberland County)

https://digitalmaine.com/alien_docs/25865/thumbnail.jp

The complex star cluster system of NGC 1316 (Fornax A)

This paper presents Gemini-$gri'$ high quality photometry for cluster candidates in the field of NGC 1316 (Fornax A) as part of a study that also includes GMOS spectroscopy. A preliminary discussion of the photometric data indicates the presence of four stellar cluster populations with distinctive features in terms of age, chemical abundance and spatial distribution. Two of them seem to be the usually old (metal poor and metal rich) populations typically found in elliptical galaxies. In turn, an intermediate-age (5 Gyr) globular cluster population is the dominant component of the sample (as reported by previous papers). We also find a younger cluster population with a tentative age of $\approx$ 1 Gyr

Alien Registration- Sesto, Maria (Portland, Cumberland County)

https://digitalmaine.com/alien_docs/25865/thumbnail.jp

"Magic" numbers in Smale's 7th problem

Smale's 7-th problem concerns N-point configurations on the 2-dim sphere which minimize the logarithmic pair-energy V_0(r) = -ln r averaged over the pairs in a configuration; here, r is the chordal distance between the points forming a pair. More generally, V_0(r) may be replaced by the standardized Riesz pair-energy V_s(r)= (r^{-s} -1)/s, which becomes - ln r in the limit s to 0, and the sphere may be replaced by other compact manifolds. This paper inquires into the concavity of the map from the integers N>1 into the minimal average standardized Riesz pair-energies v_s(N) of the N-point configurations on the 2-sphere for various real s. It is known that v_s(N) is strictly increasing for each real s, and for s<2 also bounded above, hence "overall concave." It is (easily) proved that v_{-2}(N) is even locally strictly concave, and that so is v_s(2n) for s<-2. By analyzing computer-experimental data of putatively minimal average Riesz pair-energies v_s^x(N) for s in {-1,0,1,2,3} and N in {2,...,200}, it is found that {v}_{-1}^x(N) is locally strictly concave, while v_s^x(N) is not always locally strictly concave for s in {0,1,2,3}: concavity defects occur whenever N in C^{x}_+(s) (an s-specific empirical set of integers). It is found that the empirical map C^{x}_+(s), with s in {-2,-1,0,1,2,3}, is set-theoretically increasing; moreover, the percentage of odd numbers in C^{x}_+(s), s in {0,1,2,3}, is found to increase with s. The integers in C^{x}_+(0) are few and far between, forming a curious sequence of numbers, reminiscent of the "magic numbers" in nuclear physics. It is conjectured that the "magic numbers" in Smale's 7-th problem are associated with optimally symmetric optimal-energy configurations.Comment: 109 pages, of which 30 are numerical data tables. Thoroughly revised version, to appear in J. Stat. Phys. under the different title: `Optimal N point configurations on the sphere: "Magic" numbers and Smale's 7th problem

[Et4N]2[TCNE]2 (TCNE = tetracyanoethylene) - an example of an exceptionally long 2.827 Ã CC bond

Journal ArticleInterest in organic compounds exhibiting unusually long CC bonds has been the subject of several recent studies.1-3 The longest sp3-sp3 C-C single bond reported to date is 1.73 A°,1,2 whereas several [TCNE]22- (TCNE = tetracyanoethylene) dimers have been recently reported to form cation-assisted, long, two-electron (pi*-pi*) CC bonds involving four carbon atoms. These CC bonds range from 2.833 to 3.09 A°. The cations range from electrostatically bonded Tl+4 and K+5 to large, bulky, non-coordinating cations such as [Cr(C6H6)2]+,6 [Fe(C5H4)2C3H6]+,7 and [TDAE]2+ [TDAE = (Me2N)2- CC(NMe2)2].4,8 Herein we report the structure, IR and UV-Vis spectroscopic properties of [Et4N]2[TCNE]2, a new example of the [TCNE]22- dimer, which exhibits the shortest (pi*-pi*) CC bond for this family of compounds

Isolation of two salts from the reduction of TCNE with [(n-C3H7)4N]I. A further example of long 2.87 Ã pi-C-C bonding in pi-[TCNE]22-

Journal ArticleReduction of tetracyanoethylene, TCNE, with tetrakis(n-propyl)ammonium iodide, [Pr4N]I, results in a new example of long pi*-CC bonded pi-[TCNE]22- dimers with a 2.870(4) A(°) intradimer CC bond, which is structurally and spectroscopically characterized. This reaction also results in isolation of [Pr4N]2[TCNE][I3] possessing isolated [TCNE][I3] possessing isolated [TCNE].- radical anions